Mixture Preparation Research Articles

Feeding system for cattle based on a wheeled robotic feeder

BACKGROUND:An analysis of the current state of production of dairy cattle products shows that the effective development of this industry can only be ensured at a breakthrough technological level. There is a wide variety of automatic feeding systems (AFS) on the market, differing in the level of automation, technical complexity and other parameters. They are actively used on foreign farms, however they are not widely used in Russia, mainly because of their high cost.
 AIMS:Development of a conceptual model of an automatic cattle feeding system based on a wheeled robotic feeder for servicing animals on domestic farms and plants.
 METHODS:The development was based on the following studies: the analysis of products made by manufacturers of systems for the preparation and distribution of feed mixtures at cattle farms; studying the works of foreign scientists devoted to the research of automatic feeding systems; modeling the operation of a robotic feeder and a mobile feed mixer-distributor using the developed mathematical apparatus based on graph theory; the experiments carried out at Russian farms with functioning automatic feeding systems and at farms that are potential consumers of these technologies.
 RESULTS:The paper presents the results of statistical processing of information obtained during the review of robotic feeders made by the worlds leading manufacturers. It is noted that the existing AFSs are suitable for relatively small European farms. For Russian farms, capable to contain 800 or more cows, the structure of the AFS with two main configurations is proposed. A description of each of the configurations is given, the schematic implementation plan for one of the configurations is given.
 CONCLUSIONS:The proposed AFS makes it possible to effectively use robotic feed dispensers with a relatively small amount of required technological equipment. Its efficiency increases with an increase in the number of livestock serviced, especially in farms with combined animal husbandry, as the specific costs of technological equipment per head decrease.

Calibrating and Validating the MFI-UF Method to Measure Particulate Fouling in Reverse Osmosis.

This study aimed to calibrate and validate the MFI-UF method in order to ensure the accuracy of particulate fouling measurements in RO. Firstly, the MFI-UF calibration was examined using two solutions of standard particles (dextran and polystyrene). Two main criteria were investigated: (i) MFI-UF linearity with particle concentrations at both low and high ranges of fouling potential and (ii) the reproducibility of MFI-UF linearity. Dextran solutions showed a strong MFI-UF linearity over the entire range of measured MFI-UF. However, the linearity was not reproducible, and different batches of dextran prepared under the same conditions produced very variable results. For polystyrene solutions, the MFI-UF linearity was verified at the higher range of MFI-UF (>10,000 s/L2), while the MFI-UF at the lower range (<5000 s/L2) appeared to be underestimated. Secondly, MFI-UF linearity was investigated using natural (surface) water under a wide range of testing conditions (at 20-200 L/m2·h using 5-100 kDa membranes). Strong MFI-UF linearity was obtained over the entire range of measured MFI-UF (up to 70,000 s/L2). Thus, the MFI-UF method was validated to measure different levels of particulate fouling in RO. However, future research focusing on MFI-UF calibration is still required through the selection, preparation, and testing of heterogeneous mixtures of standard particles.

Enhanced Photocatalytic Activity of Cu2O/ZnO/GO Nanocomposites on the Methylene Blue Degradation

This study synthesized nanocomposite photocatalyst materials from a mixture of Cu2O nanoparticles, ZnO nanoparticles, and graphene oxide (GO) through coprecipitation and hydrothermal methods. This study aims to determine the optimum composition of Cu2O/ZnO/GO nanocomposites in degrading methylene blue. The nanocomposite was synthesized in two steps: 1 the synthesis of Cu2O and ZnO nanoparticles through the coprecipitation method and the preparation of GO through the modified Hummer method. 2 The preparation of Cu2O and ZnO nanoparticles mixtures with GO through the hydrothermal method to form Cu2O/ZnO/GO nanocomposites. The adsorption-photocatalysis process of methylene blue was done with UV light from a halogen lamp. The characterization results indicated that the optimum composition was Cu2O/ZnO nanocomposite with a ratio of 1:2 and 10% of GO, which had a specific surface area of 35.874 m2 g-1, a pore radius of 19.073 nm, and a pore volume of 0.092 cm3 g-1, and a diameter crystalline of 31.19 nm. The degradation efficiency of methylene blue under UV light for 120 minutes were 82.0%, 86.0%, 91.4%, and 79.3% using the Cu2O/ZnO nanocomposites with GO of 1%, 3%, 5%, and 10%, respectively. These results indicated that Cu2O/ZnO/GO nanocomposites efficiently degrade methylene blue from textile dye waste.

Preparation, Verification and Stability of Calibration Gas Mixture of Benzene in Nitrogen

Preparation, Verification and Stability of Calibration Gas Mixture of Benzene in Nitrogen

DİSCONTİNUED HİGH-DENSİTY AND LOWDENSİTY POLYETHYLENE PURCHASE OF ENVİRONMENTALLY FRİENDLY ROAD SURFACES

This work, in order to improve the main indicators of oil-road bitumen, it is dedicated to the modification of polymer materials that have been decommissioned and turned into waste. For this purpose, "Baku 85/25" brand bitumen was selected and modified. After that, polymeasphaltoconcrete mixture obtained on the basis of changed "Baku 85/25" brand bitumen was prepared and its physical and mechanical properties were studied. The results of the analysis showed that by adding 3-5 mass parts of polymer waste to bitumen, it is possible to increase its viscosity by 2 times and its strength by 4 times. The obtained results show that the penetration of the prepared sample is 1.4 times higher than the standard, its elasticity is 4 times higher, and it is proved that the mixture has high deformation properties. As a result of our scientific research works, a new processing technology for the environmental protection of out-of-service polymer products was developed, polymer scraps of 0.16-0.18 mm size were purchased, and "Baku 85/25" brand bitumen was modified with this polymer scrap. Thus, the most critical environmental problem was solved and very valuable raw materials were obtained. Based on the obtained results, it was proposed to use "Baku 85/25" brand bitumen modified with polymer in the preparation of the asphalt-concrete mixture

ДОСЛІДЖЕННЯ ВПЛИВУ ПОЛІМЕРНИХ ДОБАВОК НА ВЛАСТИВОСТІ ПОРИЗОВАНИХ СУХИХ БУДІВЕЛЬНИХ СУМІШЕЙ

The theoretical prerequisites for obtaining porous mortars modified with polymer additives based on dry construction mixturesand experimental studies on determining the influence of these additives on the parameters of mixture preparation and on the rheological and physico-mechanical properties of porous mortar are presented.The article presents the results of theoretical-experimental studies of the complex influence of polymer additiveson the properties of dry construction mixtures made with an activated mineral component -Portland cement and mineral fillers and microfillers based on local raw materials. The main results of experimental studies of porous compositions of dry mixtures for floors with the addition of polymer additives are given.It was established that the modification of dry building mixtures based on Portland cement and activated mineral fillers withpolymer additives allows to increase by 25-40% the physical and mechanical properties of hardened solutions for floors and to obtain compositions with a compressive strength of up to 16.3 MPa, as well as to significantly improve the rheology of the mortar mixtures and reduce shrinkage phenomena when introducing corrosive additives without increasing the water consumption of the mixture and overusing the binder

A comparative life cycle energy and green house emissions of natural and artificial stone-manufacturing phase

The natural stone industry in many countries plays an essential role in its cultural heritage, history and economy. However, the stone industry consumes large amounts of energy in the production phase. The total energy in the natural stone production is a collective summation of energy levels consumed in each phase of production, starting from stone quarries or from mixture preparation to finally produce natural or artificial stone as an end product. The study aims at evaluating the total embodied energy of the stone industry in Palestine to further conduct a comparative Life Cycle Assessment (LCA) for both energy levels consumed in the manufacturing of natural and artificial stone. Personal interviews, observations, and stone quarry sites and workshops visits were used to collect data in Hebron – south of the West Bank. The results have shown a more sustainable production of artificial stone over natural stone in terms of energy consumption; and the (GHG) emissions accordingly as the amounts of energy for natural and artificial stone manufacturing were 120 MJ/m2 and 70.71 MJ/m2 respectively. As a conclusion, the study proves that natural stone (limestone) manufacturing produces more (GHG) emissions than the locally made artificial stone manufacturing in the study context under the studied circumstances. The environmental impact can be decreased through locating the workshops near the quarries and the sourcing points of raw materials. In addition, this can be obtained by depending on electrical vehicles and using green energy sources.

Improvement of the design of the feed mixer and analysis of its performance

BACKGROUND: It has been proven by science and practice that feeding animals with complete feed mixtures can increase the productivity of feed. The preparation of loose feed mixtures has become most widespread. The analytical review of scientific and research works in the field of machinery and technology for the preparation of complete feed mixtures showed the advantage of using batch feed mixers. This is related to the fact that due to the circulation of feed components in a mixer, high quality of feed mixtures is achieved. At the same time, the issue of research and selection of reasonable parameters for improved ideological options in the direction of reducing energy and resource costs remains relevant.&#x0D; AIMS: Improvement of the design of a vertical batch mixer, elimination of cases of delay in unloading the finished mixture, which negatively affects productivity and the energy, labor and material costs associated with it.&#x0D; METHODS: The object of the research is the technology and design of a batch feed mixer. The cyclic and hourly average productivity of the mixer is studied. Mathematical expressions that describe the dependence of the loading and unloading duration on the mixer tankage are given. The influence of the mixer tankage on the mixer performance, expressed with a special coefficient, is analyzed. The coefficient range, which positively affects the performance of the facility, has been determined.&#x0D; RESULTS: It has been established that with the constructive and technological improvement of mixers and ensuring the proper operation, the tankage does not serve as the main factor for productivity increase.&#x0D; CONCLUSIONS: The maximum productivity of the vertical batch mixer is mainly ensured with the number of cycles of the auger and with the periodic forced supply of the mixture, whereas the quality of mixing depends on the angle of the vane opener.

Performance of Excavated Sulfur-Rich Soil Stabilized with Binder: A Field Study of Mixing Efficiency

In this study, a mixing procedure of sulfur-rich soil and cement-based binder to enhance the soil’s unconfined compressive strength (UCS) was tested in field conditions for geotechnical applications. The focus was to evaluate uniformity of industrial size soil-binder mixture, blended by existing method. This paper outlined sampling strategy and the number of samples needed for a valid uniformity evaluation. Moreover, this study emphasized the difference between field mixing and laboratory mixture preparation by comparing UCS of stabilized soil samples in the field and UCS of corresponding samples mixed and prepared in the laboratory environment. In the field, soil and cement were blended in two to four stages with 5% and 7% cement—the percentages being based on the soil’s dry weight under field conditions. Samples were taken from the field mixtures after each stage. Since the number of samples needed to be representative of mixture characteristics for large-scale mixing is not standardized, this field experiment included two phases. The first phase was dedicated to finding a sampling strategy for a large soil pile along with measuring UCS of collected samples. In the second phase, sample collection was conducted based on the results of sampling strategy from the first phase. In the laboratory, samples with percentages of binder similar to the amount of binder in the field were also prepared. Both field and laboratory samples were prepared using the tapping method in the laboratory for UCS test. Samples were cured under similar conditions for 28 days. The results showed that the uniformity of mixture improved after each additional mixing stage. In addition, while spots with low UCS were observed in the second mixing step, these spots were eliminated in the third mixing step, and results of the UCS tests were comparatively uniform. Moreover, comparison of the samples revealed that the UCS of the laboratory mixture is higher than that of the field mixture. This showed that even though the UCS is a good standard for comparing the strength of different soils stabilized with different percentages or types of binders in the field mixing, the actual strength of the stabilized mixtures under field circumstances is lower than that in laboratory prepared mixtures.

Mixing of heat-insulating mixtures in pneumatic mixer with spiral energy carrying tube

Introduction. Mixing of dry components in mixers is one of the most important stages of any technological process in the manufacture of a composite material. To date, various technologies use a wide variety of mixing equipment, which is characterized by different principles of mixing and design solutions. Of particular interest for the preparation of high-quality and homogeneous mixtures for heat-insulating purposes is a pneumatic mixer with a spiral energycarrying tube. The article presents the results of studies using the method of mathematical planning of the fullfactor ПФЭЦКРП24 experiment, which makes it possible to most adequately assess the ongoing processes while minimizing systematic errors.Materials and methods. In the work, ЦЕМ 0 42,5Н ГОСТ 31108–2020 Portland cement with a specific surface area of 308 m2 / kg, sand of the Volsky deposit were used as raw materials for testing. Expanded vermiculite obtained as a result of heat treatment of natural vermiculite at a temperature of about 700°C was used as a light filler.Results. Heat-insulating mixtures prepared in a pneumatic mixer with a spiral energy-carrying tube ensure the production of heat-insulating mortars with stable density values of 1420 kg/m3, having sufficient compressive strength of 3.3 MPa, and guarantee high heat-shielding properties in building structures.Conclusion. The developed design and the conducted studies made it possible to establish the high efficiency of the proposed mixer, which provides a uniform distribution of the particles to be mixed, high homogenization and the creation of conditions for accelerating the physicochemical interactions in the created mixture with subsequent mixing of the prepared mixture with water and the formation of the required internal structure of the created composites.

Justification of the impeller speed choice for optimization of the continuous mixing mode in a facility for preparation of liquid feed mixtures

BACKGROUND: In the coming years, most of the main livestock production will be produced on farms under their collective lease, as well as on individual farms, which will ensure intensive development of the industry.&#x0D; AIMS: The paper is devoted to the study of the liquid feed mixtures preparation under different impeller speeds, under different temperatures of the liquid and with further parameters optimization.&#x0D; MATERIALS AND METHODS: The experimental facility for the liquid feed mixtures preparation is a multifunctional technical equipment, capable of performing following 3 functions: dosing of material (the whole milk replacer), liquid supply (the pumping function) and mixture preparation (the mixer function).&#x0D; RESULTS: The study of facilities, based on blade pumps, revealed that the rotational speed n in the range of 1750 to 3000 min-1 is not always effective. Then, the indicators of performance or mixture supply are bigger for these values. Thus, the experiment is carried out based on the synchronism of the rotational speeds of the electric motor and the impeller: n = 750, 1000, 1250, 1500 and 1750 min-1. The application of an asynchronous electric motor implies taking account of slip s being 23%.&#x0D; CONCLUSIONS: The study of the mixing facility at the continuous mixing mode shows that it is not necessary to take the mixing time into account with given design parameters, as the mixture processing occurs instantly, for a very short time intervals Tc = 0.020.006 s. Experimental studies show that the impeller speed under different temperatures of the liquid affects the degree of the mixture homogeneity, while the number of fixed blades is also considered. Thus, in the continuous mixing mode, the degree of homogeneity Ѳ is 85.2% for a speed n = 9501490 min-1, while the water temperature t is 2024 C.

Evaluation of Biomass Solid Waste as Raw Material for Preparation of Asphalt Mixture

At present, the resource utilization of solid waste in China is facing prominent problems such as high production intensity, insufficient utilization, and low added value of products. The preparation of biomass composites from biomass solid waste and plastic solid waste reduces not only environmental pollution and energy consumption but also promotes the high-value utilization of solid waste. So, the characterization and preparation experiments of samples with two different biomass are carried out. The wheat straw fiber and corn straw fiber were added into the bio-asphalt mixture with the content of 0.1%, 0.2%, 0.3%, and 0.4%, respectively, with the content of 9% and 12% bio-heavy oil. The physical properties and rheological properties of asphalt were analyzed and evaluated by three indexes and a dynamic shear rheological test. Through the rutting test and immersion Marshall test, high-temperature performance and biological asphalt mixture’s water stability were evaluated. The results show that straw fiber can improve bio-asphalt mixture’s road performance, especially the performance of high-temperature rutting. When the fiber content of bio-asphalt with 9% bio-heavy oil content is 0.3%, the physical properties and rheological properties of bio-asphalt are the best. Corn straw fiber’s influence on bio-asphalt mixture was better than that of wheat straw fiber.

Ultra-High-Performance Concrete (UHPC) - Applications Worldwide: A State-of-the-Art Review

Research is in progress on the applications of ultra-high performance concrete (UHPC) as a new additive material in construction technology. Over the last twenty years’ significant improvements have been achieved in mechanical properties of UHPC, such as its strength, workability, and ductility, with further improvements made in self-placing properties, higher density, and durability compared with normal concrete. One of the biggest advantages offered by ultra-high performance concrete over normal concrete is the possibility to minimize the cross-sectional dimensions of the structural elements. UHPC can be used to provide significant long-span members, whilst also showing less variation, creep, and drying shrinkage compared to conventional concrete. After many years of development and research into UHPC’s properties, it is being used in commercial applications to meet the rising demand for quality constructions. Many projects in the world started using UHPC for different construction objectives such as long spans, columns, jacketing, rain-screen cladding systems, panel systems, façades, etc. Furthermore, there are not enough sources in the literature describing mixture design, preparation, and curing. This research gives an overview of the uses of UHPC in structural and architectural applications.

Effect of Ultrasound-Assisted Freezing on the Crystal Structure of Mango Sorbet

In this study, the effect of ultrasound-assisted immersion freezing (UAF) of mango sorbet in comparison to conventional freezer freezing, on freezing course and created crystal structure, was studied. The scope of work included the preparation of a sorbet mixture prepared on the basis of frozen mango fruit with the addition of locust bean gum (LBG), guar gum and a commercial mix of carrageenan without the addition of stabilizers, and freezing it using a conventional freezer and ultrasound-assisted freezing equipment, with variable operating parameters (21.5 kHz and 40 kHz—continuous or chopped mode). Then, the freezing time and the crystal structure of the frozen samples (a microscopy analysis) were examined. US-assisted freezing reduced the time of the process for stabilized samples of the sorbet. It was also proven that, proper stabilization with the combination of US treatment results in the formation of favorable crystal structure. Stabilized sorbet subjected to US action at a frequency of 21.5 kHz in chopped mode was characterized by the most uniform crystal structure, consisting of crystals with the smallest diameters among all the tested samples; the equivalent diameter was 9 µm, while for the stabilized control it was 25 µm.

Laser and pre-chamber ignition, combustion and flame propagation characteristics of CH4/air mixtures in a constant volume combustion chamber

The most important stages determining the qualitative and quantitative characteristics of a combustion process are mixture preparation, ignition, combustion itself and pollutant emissions. Among these, the ignition phenomenon stands out in terms of ensuring a reliable operation under every working condition (which also affects subsequent stages). In this study, the influence of the properties and the type of the ignition source on combustion and flame propagation characteristics of methane/air mixtures were investigated by using a passively Q-switched Nd:YAG crystal laser and a pre-chamber ignitor in a constant volume combustion chamber. The number of consecutive pulses and the air-fuel-equivalence ratio are studied parameters. With the laser ignition system, it was possible to ignite fuel-air mixtures at very lean conditions. However, as flow conditions in the combustion chamber varied due to the protruding part of the pre-chamber ignitor, ignition possibility decreased and combustion metrics worsened. The number of pulses affected combustion parameters such as the ignition delay time, the combustion duration, the rate of pressure rise etc. in a non-monotonic manner. Deteriorations and improvements on such parameters were detected depending on the air–fuel-equivalence ratio λ.

Numerical modeling of hydrogen mixing in a direct-injection engine fueled with gaseous hydrogen

Hydrogen is considered as one of the most promising options to achieve effective decarbonization of the energy and transportation sectors. As such, it has recently been receiving increasing attention because of its promising potential as an energy carrier for advanced energy and propulsion systems. With a focus on internal combustion engines, direct injection (DI) of gaseous hydrogen during the compression stroke offers great potential for high engine efficiency and specific power while reducing the risk of backfiring and pre-ignition issues. Therefore, many experimental and numerical efforts have recently been dedicated to understanding the physical and chemical behaviors of hydrogen in engine during mixing and combustion. This study focuses on computational fluid dynamics (CFD) modeling of the hydrogen DI process in a hydrogen optical research engine. Under the conditions studied, gaseous hydrogen is injected into the combustion chamber via a centrally located single-hole injector at a pressure of 100 bar. Two configurations, namely low- and high-tumble, are investigated to understand the impact of different in-cylinder flow patterns on the fuel-air mixture preparation. Simulations are carried out using the commercial CFD software CONVERGE. The in-cylinder turbulence is modeled with an unsteady Reynolds-averaged Navier-Stokes (URANS) formulation closed by the renormalization group (RNG) k-ε model. Several numerical methods and model constants, including but not limited to turbulent Schmidt number, are evaluated. The numerical results are systematically compared against experimental measurements of velocity and hydrogen concentration fields on the vertical center plane to assess the performance of the CFD model, unveil the physics of hydrogen mixing, and establish best practices for modeling hydrogen DI under relatively high injection pressure conditions.

Logical-probabilistic model of the reliability of means for preparing and distributing fodder

Countries with a developed agricultural sector of the economy use modern advances in industry and computer technology in precision animal husbandry. At the current stage of animal husbandry development, both in global practice and in Ukraine, for the preparation of fodder mixtures, means for preparation and distribution of fodder are becoming more and more widespread, which combine the operations of loading, grinding, mixing, transportation and dosed distribution of fodder mixtures. The purpose of the presented article is to assess and ensure the reliability of the operation of the means for preparing and distributing fodder due to the logic-probabilistic modeling of failures of the feed mixture unloading mechanism as a subsystem of the "Man-Machine-Environment" technical system. The results of theoretical and experimental research are a continuation of previous work and are aimed at increasing the efficiency of use and ensuring the reliability of machines and equipment for animal husbandry. The obtained results of theoretical and experimental studies of reliability based on logical-probabilistic modeling of means for preparing and distributing feed as complex technical systems depending on the influence of the components "man-operator", "machine", "environment". The shortest paths of failures and the minimum cross-sections of their prevention for the research objects were analyzed. In order to prevent the failure of the human-operator component of the system, it is necessary to provide sufficient qualification of the personnel, foresee the possible occurrence of errors and ensure their timely elimination. In order to prevent failures of the feed mixture unloading mechanism, it is necessary to timely control and adjust the condition of parts during operation and when restoring performance. It has been established that the probability of failure of the mechanism will be less important, provided that the probability of elimination of failures due to insufficient qualification of the operator and failure of drive parts is 0.2. An increase in the probability of failure of the operator under the condition of insufficient qualification from 0.5 to 0.9 will lead to an increase in the probability of failure as a result of a change in the conveyor tension and the impossibility of adjusting the conveyor tension, and at 0.9 the probability of failure of the mechanism will be 0.046. The practical significance of the results lies in the possibility of investigating the probability of failure of the feed mixture unloading mechanism based on the reliability of the components of the means for preparing and distributing feed, including the hydraulic cylinder, drive parts, and conveyor belts

Utilisation of aged and unaged basic oxygen furnace steel slag aggregates in pavement quality concrete

ABSTRACT The study presented in the paper evaluated the properties of pavement quality concrete (PQC) containing coarse aggregates made from aged and unaged basic oxygen furnace (BOF) slag. Workability, air content, strength, drying shrinkage, expansion, abrasion resistance and expansive potential of PQC were evaluated. Air content and workability of fresh slag concrete increased marginally. Compressive and flexural strength of the concrete containing aggregates of aged and unaged slag was observed to be less than the strength of normal concrete. The reduction in strength of concrete containing aged slag aggregates was more as compared to the concrete containing unaged slag aggregates due to the presence of a dusty coating around the aged aggregates. The drying shrinkage of the concrete increased with the content of steel slag aggregates. The abrasion resistance of the slag concrete was found to be better than the abrasion resistance of conventional concrete. Deterioration of slag concrete was not observed due to normal water curing up to 90 days. However, accelerated aging of concrete in water at 70°C resulted in the localised cracking and eruptions due to expansion. The study showed that, aged as well as unaged slag aggregates may be used for the preparation of concrete mixtures of required properties for road construction.

Preparation of a quantum degenerate mixture of Na23K40 molecules and K40 atoms

We report on the preparation of a quantum degenerate mixture of $^{23}\mathrm{Na}\phantom{\rule{0.16em}{0ex}}^{40}\mathrm{K}$ molecules and $^{40}\mathrm{K}$ atoms. A deeply degenerate atomic mixture of $^{23}\mathrm{Na}$ and $^{40}\mathrm{K}$ atoms with a large number ratio (${N}_{F}/{N}_{B}\ensuremath{\approx}6$) is prepared in a large-volume optical dipole trap. About $3.0\ifmmode\times\else\texttimes\fi{}{10}^{4}\phantom{\rule{0.16em}{0ex}}^{23}\mathrm{Na}\phantom{\rule{0.16em}{0ex}}^{40}\mathrm{K}$ ground-state molecules are created through magnetoassociation followed by stimulated Raman adiabatic passage. The pure molecular gas is in the moderately degenerate regime. In the atom-molecule mixture, the elastic collisions provide a thermalization mechanism for the molecules. The calculated thermalization time constant is smaller than the lifetime of the molecules in the atom-molecule mixture. This indicates that the molecules may reach thermal equilibrium due to elastic atom-molecule collisions before notable losses take place. In a few tens of milliseconds, the degeneracy of the molecules is maintained. This time interval is long enough for the study of strongly interacting atom-molecule mixtures and the production of ultracold triatomic molecular gases.

Problems of the safe use of modern cement materials in the practice of drinking water supply

Introduction. Recently, there have been increasing changes in the technology of preparation of cement mixtures and concrete, the use of new components in their composition, since traditional materials are not quite suitable for the construction of hydraulic structures, including the internal coating of pipes and drinking water tanks. However, in addition to improving the characteristics of cement mixtures, additives can have a negative impact on the environment and human health by leaching out of cement into drinking water. The definition of only the main components specified in the “Universal sanitary-epidemiological and hygienic requirements for goods subject to sanitary-epidemiological supervision (control)” (hereinafter - the Universal Requirements) does not provide complete information about the chemical safety of cement materials during the hygienic assessment. Materials and methods. There were studied eleven samples of cement mixtures from various manufacturers repaired of reinforced concrete products and structures of general and special purpose, including those in contact with drinking water, and used for the sanitation of the internal surfaces of steel pipelines (including hot water supply systems) and repair and restoration work. The evaluation of samples was carried out taking into account Universal requirements, and indicators that are not mandatory for the evaluation of these materials were investigated. Results. Hygienic assessment of cement mixtures showed lithium to be detected in some extracts in concentrations from 20 mg/L to 0.18 mg/L, which is 666 times higher than its maximum permissible concentration - 0.03 mg/L. Also, two samples showed a slight excess of the permissible chromium concentration - 0.065 mg/L and 0.09 mg/L (MPC &lt; 0.05). Iron and zinc in insignificant concentrations were found in aqueous extracts; in one of the samples a 2-fold excess of the manganese concentration was observed. One water extract contains silicates at a concentration of 34.24 mg/L, which exceeds their permissible levels in drinking water. The analysis also identified a number of organic compounds related to oxygen-containing compounds (alcohols, phenol derivatives, ketones, esters, phthalates), for most of which no MPC has been established. Limitations. The study was carried out on eleven samples of cement mixtures under standard conditions: infusion in model media for 30 days at room temperature in the ratio: 1 cm2 of the sample surface to 1 cm3 of water. Sampling was carried out on the Days 1, 3, 5, 10, 20 and 30 of research, without changing the test water. It is necessary to conduct similar studies under experimental conditions close to the operating conditions of these materials. Conclusion. Assessing the efficiency of migration from cement-bound materials, it is necessary to take into account their capillary-porous structure on the one hand and the ability to improve the coating properties over time by converting calcium hydroxide present in freshly applied cladding into denser calcium bicarbonate. The migration of chemicals from cement-bound material is to be evaluated by taking into account the specific conditions of their use in the practice of drinking water supply, and the assessment of the additives introduced should be carried out on test cement samples, since it is impossible to theoretically calculate the migration rate of the components from the finished material.